On Instagram and Reddit, people share photographs of clusters that make them anxious, obsessed and even nauseated. Many images show holey foods or clusters of seeds, like aerated chocolates, the innards of a red bell pepper, and bubbles rising up in pancakes while they cook.

"I don't like the holes in crumpets or sponges or Swiss cheese," @CourtneySGray said on Twitter. "They all make me shudder and panic."

The standard litmus test for trypophobia seems to be a photograph of lotus seeds. And I have to admit, these pictures can give me the heebie-jeebies if I think about them long enough.

But in Southeast Asia, people eat these like peanuts. They just peel the pods and pop the seeds in their mouth. And down in New Orleans, people harvest lotus from the bayous and then fry up the seeds.

So I'm not convinced about this trypophobia. From the comments on Facebook, it's clear that many people didn't even realize these photographs bothered them until they stumbled upon them on Google.

Is there really a common phobia to lotus and melon lurking in our society, or could this just be some modern-day phenomenon fueled by social media and the power of suggestion?

Psychiatrist Carol Mathews of the University of California, San Francisco, who specializes in anxiety disorders, thinks it's mostly the latter.

She's never heard of trypophobia, and from looking at the comments on the Web, she doesn't think most people have a real phobia — or an intense fear — to these objects. Instead, they simply find the images disgusting or yucky.

Mathews thinks this response is probably due to a psychological concept known as priming: You're asked if the lotus photo makes you feel itchy, so it's more likely to stir up an itch or two.

"We all have random skin sensations, but we normally filter them out," she tells The Salt. It's "like background noise — our brains have taught us not to listen to it. But if we're asked to pay attention to our skin, then we start to feel all these little itches."

Research psychologist Arnold Wilkins at the U.K.'s University of Essex has been investigating the phenomenon, and he thinks he might know what's going on. In images that set off this repulsion, the pattern of contrast is similar to that found in photographs of extremely poisonous animals — like box jellyfish, king cobras and Brazilian wandering spiders. Wilkins speculates that we humans are especially good at picking out these patterns because they help us spot dangerous animals that might otherwise blend with the background.

It's a tidy, evolution-based theory, but Mathews isn't buying it.

Intermixing truly yucky pictures of parasites and skin conditions with innocuous images of cantaloupes and crumpets, she says, could also make you feel grossed out by your breakfast. This is a type of conditioning, in which one emotion — disgust, uncomfortableness — gets associated with something that normally doesn't evoke that emotion.

"There might really be people out there with phobias to holes, because people can really have a phobia to anything," she says. "But just reading what's on the Internet, that doesn't seem to bewhat people actually have."

"Now that I think about cantaloupes, I feel a little disgusted, too," Mathews says. "And I really like cantaloupes."